The present invention relates to a surface reformation method of a high polymer material and, more particularly, to a surface reformation method of a high polymer material which is preferable to be used in order to improve wettability of a liquid used for temporarily immobilizing electronic parts on an electronic circuit board, the surface of which is covered by a high polymer material layer. The invention also relates to improvement of wettability of a liquid used for temporary immobilization of electronic parts when the electronic parts are soldered on an electronic circuit board according to a fluxless reflow soldering.
As a conventional technique regarding a surface reformation method for wettability improvement of a high polymer material, for example, methods using an O.sub.2 asher, Ar sputter, or the like are known. In there methods, a process is performed by setting a circuit board on which a high polymer material layer to be processed is coated in a vacuum vessel, and the surface reformation is executed for the entire surface of the high polymer material on the substrate.
According to the conventional technique using, for example, the O.sub.2 asher or Ar sputtering mentioned above, the surface of the substrate can be reformed only in an atmosphere of vacuum and there is a problem such that a large-scaled apparatus including vacuum equipment, vacuum vessel, and the like is necessary. According to the conventional technique, since the surface reformation is executed for the entire surface of the high polymer material on the substrate, an area which is not necessary to be processed other than the area on which the electronic parts are temporarily immobilized on the electronic circuit board or the like is also reformed. Consequently, the liquid used for the temporary immobilization of the electronic parts wets the portion which is unnecessary for the temporary immobilization of the parts, so that there is a problem such that a large amount of liquid is wasted. As mentioned above, when the entire surface of the high polymer material on the substrate is reformed and the liquid for temporary immobilization wets even the unnecessary portion, even if the parts are temporarily immobilized, the parts are moved from positions of the temporary immobilization at the time of reflow soldering, so that the object of the temporary immobilization cannot be achieved. Particularly, when the size of the substrate is equal to 50 mm.times.50 mm or larger, since the liquid for temporary immobilization tends to gather in the center and the temporarily immobilized parts easily move, it is not preferable. Hitherto, a flux for soldering has been commonly used in the temporary immobilization of the parts in the reflow soldering and the parts are not moved from the positions of the temporary immobilization. In case of performing the reflow soldering without using the flux, however, when the liquid for temporary immobilization wets the unnecessary portion, the object of the temporary immobilization is not achieved as mentioned above. It is, therefore, conventionally difficult to solder the electronic parts at predetermined positions on the electronic circuit board by performing a fluxless reflow soldering.